Abstract Mn-activated yttria (Y 2O 3:Mn) phosphor thin films, consisting of monoclinic Y 2O 3 host material, were prepared by r.f. magnetron sputtering. High-luminance yellow photoluminescence and electroluminescence emissions were obtained using Y 2O 3:Mn thin films prepared with a Mn content of 2 at.% at a substrate temperature of approximately 350 °C and postannealed at approximately 1020 °C in an Ar atmosphere. The obtainable electroluminescent (EL) characteristics of Y 2O 3:Mn thin-film EL (TFEL) devices were mainly related to the crystallinity of the thin-film emitting layers used in the devices. The obtained maximum luminance and luminous efficiency increased as the crystallinity of the monoclinic Y 2O 3:Mn thin-film emitting layers was improved. A luminance of 5110 cd/m 2 was obtained in a 1 kHz-driven TFEL device fabricated with monoclinic Y 2O 3:Mn phosphor thin film prepared under the optimized conditions.